Types of band-saw machines include a horizontal band-saw machine and a vertical band-saw machine. A band-saw blade used in band-saw machines is configured in an endless manner, by joining both end portions of a band-shaped saw blade by welding. A technique of swinging cutting has been developed in order to reduce a cutting length to perform cutting of a workpiece, at the time of cutting work of a workpiece is performed using such an endless band-saw blade. This technique is disclosed in, for example, Japanese Patent Application Laid-open Publication No. JP-A S56-107825.
For example, in a horizontal band-saw machine, a workpiece is cut by the swinging cutting while alternately inclining a band-saw blade to a state of diagonally right down and diagonally left down. That is, cutting work is performed on a workpiece by alternately repeating right down inclination and left down inclination of a saw blade housing including the band-saw blade slowly to incline the band-saw blade in the state of diagonally right down or diagonally left down. There has also been developed a configuration where, when swinging cutting is performed, a band-saw blade is inclined in a state of diagonally right down and diagonally left down by moving a guide roller included in a band-saw blade guiding apparatus that performs guiding of the band-saw blade in a cutting direction. This technique is disclosed in, for example, Japanese Patent Application Laid-open Publication No. JP-A 2003-305613.
There is also a technique for adopting a configuration where a wave-shaped undulation is formed on a back portion of a band-saw blade for performing swinging cutting such as the one described above, and when a top portion of the undulation is positioned at one of band-saw blade guiding apparatuses, a bottom portion thereof is positioned at the other apparatus, to incline the band-saw blade to a state of orthogonally right down or orthogonally left down, thereby performing swinging cutting of a workpiece. This technique is disclosed in, for example, Japanese Patent Application Laid-open Publication No. JP-A H9-300131.
Generally, gear cutting work is performed to form a band-saw blade using a milling cutter in a gear cutting machine that is most suitable for mass production. Accordingly, a band-saw width precision of the band-saw blade (a degree of variations of values obtained by measuring many distances from a distal end of a tooth tip formed according to the gear cutting work to a back face of the band-saw blade) is determined depending on a precision of the gear cutting machine, a precision of the milling cutter and the like. However, the band-saw width precision of the band-saw blade obtained by the work has variations in a range from 0.03 to 0.05 mm, even if the blade is a favorable one.
Several hundred or more tooth tips are formed on one band-saw blade. A cutting amount per one tooth on the band-saw blade is examined below. When a height of a workpiece in a cutting direction is represented as Hmm, a pitch of tooth tips of the band-saw blade is represented as Pmm, a rotational velocity (sawing rate) of the band-saw blade is represented as Vm/min, and a cutting time is represented as tmin, the cutting amount amm per one tooth is expressed by the following equation.a=(H×P)/(1000×V×t)mm
Next, in order to conduct specific calculations, representative samples are extracted from a cutting condition table described in a blade (band-saw blade) catalogue for year 2000 issued by AMADA Co. Ltd., Japan, who is the present applicant, and the calculations are performed.
(1) A pitch P of tooth tips of a band-saw blade conforming to S45C(JIS) φ100 is set to 7.3 mm.
Rotational velocity V of band-saw blade: 48 to 72 m/min
Cutting time t: 1.5 to 2.2 min
The minimum value of a cutting amount “a” per one tooth in this conditions is(100×7.3)/(1000×72×2.2)=0.0046 mm,
and the maximum value thereof is(100×7.3)/(1000×48×1.5)=0.0101 mm.
(2) A pitch P of tooth tips of a band-saw blade conforming to SUS304(JIS) φ500 is set to 19.5 mm.
Rotational velocity V of band-saw blade: 17 to 26 m/min
Cutting time t: 90 to 168 min
The minimum value of a cutting amount “a” per one tooth in the conditions is(500×19.5)/(1000×26×168)=0.0022 mm,
and the maximum value thereof is(500×19.5)/(1000×17×90)=0.0064 mm.
As understood from the above, an average cutting amount per one tooth of a band-saw blade is generally 0.01 mm or less.
However, as described above, the band-saw width precision of the band-saw blade includes variations in a range from 0.03 to 0.05 mm, even if the blade is a favorable one. That is, the cutting amount per one tooth is ⅓ or less of the band-saw width precision, where there is a problem that when cutting is performed in this state, only teeth with a relatively wide width of all the teeth including variations in band-saw width can work for cutting, and not all the teeth do not work.
It is easily conceived that teeth that move, but only gall a cutting face without removing chips, are present. Presumably, it is conceivable that the teeth that move in a galling manner generate uncomfortable noises and extra heat.
The present invention has been achieved in order to solve the problem, and an object of the invention is to provide a cutting method that can perform effective cutting by controlling a band-saw blade such that all teeth corresponding to a workpiece can cut in the workpiece, and a band-saw machine used in the cutting method.